France's Top 14, the world's richest rugby union championship, suffered a record deficit of 24.2 million euros ($25.5 million) last season as player salaries soared, the league said Tuesday.

"Clubs prefer to strengthen their sporting power ... to the detriment of reducing their deficits," said a report by the National Rugby League's audit department.

The Top 14 accounted for the bulk of a 33.8 million euro ­deficit for all 30 professional clubs in France, which has become an increasing magnet for foreign stars.

Average player salaries have increased 12 percent in the past season, according to the report released late Monday.

All Black Colin Slade is the latest foreign star to have signed for a French club. According to New Zealand media, he will earn 660,000 euros a season at Pau. Dan Carter and other All Blacks are also moving to France.

Salaries have "taken off" while revenues grew only 10 percent, mainly through extra television income.

Only one Top 14 club is able to fully self-finance its operation, against seven at the end of 2013-14. Three clubs have are "heavily in deficit." The league report did not name the clubs, but the Midi Olympique rugby newspaper said they are Racing Metro, Stade Francais and Castres where the owners pay for annual losses.

Top 14 attendances have also "stagnated" over the past five seasons, according to the league report. The average attendance last season was 13,538, up from 13,162 the previous season but still below the peak of 14,032 in 2010-11.